9.4 HEAD
The HEAD method is identical to GET except that the server MUST NOT
return a message-body in the response. The metainformation contained
in the HTTP headers in response to a HEAD request SHOULD be identical
to the information sent in response to a GET request. This method can
be used for obtaining metainformation about the entity implied by the
request without transferring the entity-body itself. This method is
often used for testing hypertext links for validity, accessibility,
and recent modification.
/* $begin tinymain */
/*
* tiny.c - A simple, iterative HTTP/1.0 Web server that uses the
* GET method to serve static and dynamic content.
*
* Updated 11/2019 droh
* - Fixed sprintf() aliasing issue in serve_static(), and clienterror().
*/
#include "csapp.h"
void doit(int fd);
void read_requesthdrs(rio_t *rp);
int parse_uri(char *uri, char *filename, char *cgiargs);
void serve_static(int fd, char *filename, int filesize,char *method); //11.11修改处
void get_filetype(char *filename, char *filetype);
void serve_dynamic(int fd, char *filename, char *cgiargs,char *method);//11.11修改处
void clienterror(int fd, char *cause, char *errnum,
char *shortmsg, char *longmsg);
int main(int argc, char **argv)
{
int listenfd, connfd;
char hostname[MAXLINE], port[MAXLINE];
socklen_t clientlen;
struct sockaddr_storage clientaddr;
/* Check command line args */
if (argc != 2) {
fprintf(stderr, "usage: %s <port>\n", argv[0]);
exit(1);
}
listenfd = Open_listenfd(argv[1]);
while (1) {
clientlen = sizeof(clientaddr);
connfd = Accept(listenfd, (SA *)&clientaddr, &clientlen); //line:netp:tiny:accept
Getnameinfo((SA *) &clientaddr, clientlen, hostname, MAXLINE,
port, MAXLINE, 0);
printf("Accepted connection from (%s, %s)\n", hostname, port);
doit(connfd); //line:netp:tiny:doit
Close(connfd); //line:netp:tiny:close
}
}
/* $end tinymain */
/*
* doit - handle one HTTP request/response transaction
*/
/* $begin doit */
void doit(int fd)
{
int is_static;
struct stat sbuf;
char buf[MAXLINE], method[MAXLINE], uri[MAXLINE], version[MAXLINE];
char filename[MAXLINE], cgiargs[MAXLINE];
rio_t rio;
/* Read request line and headers */
Rio_readinitb(&rio, fd);
if (!Rio_readlineb(&rio, buf, MAXLINE)) //line:netp:doit:readrequest
return;
printf("%s", buf);
sscanf(buf, "%s %s %s", method, uri, version); //line:netp:doit:parserequest
if (strcasecmp(method, "GET")&&strcasecmp(method, "HEAD")) { //11.11修改处line:netp:doit:beginrequesterr
clienterror(fd, method, "501", "Not Implemented",
"Tiny does not implement this method");
return;
} //line:netp:doit:endrequesterr
read_requesthdrs(&rio); //line:netp:doit:readrequesthdrs
/* Parse URI from GET request */
is_static = parse_uri(uri, filename, cgiargs); //line:netp:doit:staticcheck
if (stat(filename, &sbuf) < 0) { //line:netp:doit:beginnotfound
clienterror(fd, filename, "404", "Not found",
"Tiny couldn't find this file");
return;
} //line:netp:doit:endnotfound
if (is_static) { /* Serve static content */
if (!(S_ISREG(sbuf.st_mode)) || !(S_IRUSR & sbuf.st_mode)) { //line:netp:doit:readable
clienterror(fd, filename, "403", "Forbidden",
"Tiny couldn't read the file");
return;
}
serve_static(fd, filename, sbuf.st_size, method); //line:netp:doit:servestatic
}
else { /* Serve dynamic content */
if (!(S_ISREG(sbuf.st_mode)) || !(S_IXUSR & sbuf.st_mode)) { //line:netp:doit:executable
clienterror(fd, filename, "403", "Forbidden",
"Tiny couldn't run the CGI program");
return;
}
serve_dynamic(fd, filename, cgiargs, method); //11.11修改处line:netp:doit:servedynamic
}
}
/* $end doit */
/*
* read_requesthdrs - read HTTP request headers
*/
/* $begin read_requesthdrs */
void read_requesthdrs(rio_t *rp)
{
char buf[MAXLINE];
Rio_readlineb(rp, buf, MAXLINE);
printf("%s", buf); //这里的printf只是在服务端打印,客户端收不到
while(strcmp(buf, "\r\n")) { //line:netp:readhdrs:checkterm
Rio_readlineb(rp, buf, MAXLINE);
printf("%s", buf);
}
return;
}
/* $end read_requesthdrs */
/*
* parse_uri - parse URI into filename and CGI args
* return 0 if dynamic content, 1 if static
*/
/* $begin parse_uri */
int parse_uri(char *uri, char *filename, char *cgiargs)
{
char *ptr;
if (!strstr(uri, "cgi-bin")) { /* Static content */ //line:netp:parseuri:isstatic
strcpy(cgiargs, ""); //line:netp:parseuri:clearcgi
strcpy(filename, "."); //line:netp:parseuri:beginconvert1
strcat(filename, uri); //line:netp:parseuri:endconvert1
if (uri[strlen(uri)-1] == '/') //line:netp:parseuri:slashcheck
strcat(filename, "home.html"); //line:netp:parseuri:appenddefault
return 1;
}
else { /* Dynamic content */ //line:netp:parseuri:isdynamic
ptr = index(uri, '?'); //line:netp:parseuri:beginextract
if (ptr) {
strcpy(cgiargs, ptr+1); //ptr指向的是字符串的第一个字符.
*ptr = '\0';
}
else
strcpy(cgiargs, ""); //line:netp:parseuri:endextract
strcpy(filename, "."); //line:netp:parseuri:beginconvert2
strcat(filename, uri); //line:netp:parseuri:endconvert2
return 0;
}
}
/* $end parse_uri */
/*
* serve_static - copy a file back to the client
*/
/* $begin serve_static */
void serve_static(int fd, char *filename, int filesize, char *method)//11.11修改处
{
int srcfd;
char *srcp, filetype[MAXLINE], buf[MAXBUF];
/* Send response headers to client */
get_filetype(filename, filetype); //line:netp:servestatic:getfiletype
sprintf(buf, "HTTP/1.0 200 OK\r\n"); //line:netp:servestatic:beginserve
Rio_writen(fd, buf, strlen(buf));
sprintf(buf, "Server: Tiny Web Server\r\n");
Rio_writen(fd, buf, strlen(buf));
sprintf(buf, "Content-length: %d\r\n", filesize);
Rio_writen(fd, buf, strlen(buf));
sprintf(buf, "Content-type: %s\r\n\r\n", filetype);
Rio_writen(fd, buf, strlen(buf)); //line:netp:servestatic:endserve
if(strcasecmp(method,"HEAD")==0)//11.11修改处
return;
/* Send response body to client */
srcfd = Open(filename, O_RDONLY, 0); //line:netp:servestatic:open
srcp = Mmap(0, filesize, PROT_READ, MAP_PRIVATE, srcfd, 0); //line:netp:servestatic:mmap
Close(srcfd); //line:netp:servestatic:close
Rio_writen(fd, srcp, filesize); //line:netp:servestatic:write
Munmap(srcp, filesize); //line:netp:servestatic:munmap
}
/*
* get_filetype - derive file type from file name
*/
void get_filetype(char *filename, char *filetype)
{
if (strstr(filename, ".html"))
strcpy(filetype, "text/html");
else if (strstr(filename, ".gif"))
strcpy(filetype, "image/gif");
else if (strstr(filename, ".png"))
strcpy(filetype, "image/png");
else if (strstr(filename, ".jpg"))
strcpy(filetype, "image/jpeg");
else if (strstr(filename, ".mpg"))
strcpy(filetype, "video/mpg");
else
strcpy(filetype, "text/plain");
}
/* $end serve_static */
void handler1(int sig)
{
int olderrno = errno;
while (waitpid(-1,NULL,0)>0){
Sio_puts("Handler reaped child\n");
}
if(errno != ECHILD)
Sio_error("waitpid error");
Sleep(1);
errno = olderrno;
}
/*
* serve_dynamic - run a CGI program on behalf of the client
*/
/* $begin serve_dynamic */
void serve_dynamic(int fd, char *filename, char *cgiargs,char *method) //11.11修改处
{
char buf[MAXLINE], *emptylist[] = { NULL };
/* Return first part of HTTP response */
sprintf(buf, "HTTP/1.0 200 OK\r\n");
Rio_writen(fd, buf, strlen(buf));
sprintf(buf, "Server: Tiny Web Server\r\n");
Rio_writen(fd, buf, strlen(buf));
if(signal(SIGCHLD,handler1) == SIG_ERR)
unix_error("signal error");
if (Fork() == 0) { /* Child */ //line:netp:servedynamic:fork
/* Real server would set all CGI vars here */
setenv("QUERY_STRING", cgiargs, 1); //line:netp:servedynamic:setenv
setenv("REQUEST_METHOD", method, 1);//11.11修改处
Dup2(fd, STDOUT_FILENO); /* Redirect stdout to client */ //line:netp:servedynamic:dup2
Execve(filename, emptylist, environ); /* Run CGI program */ //line:netp:servedynamic:execve
}
/*Wait(NULL); Parent waits for and reaps child */ //line:netp:servedynamic:wait
}
/* $end serve_dynamic */
/*
* clienterror - returns an error message to the client
*/
/* $begin clienterror */
void clienterror(int fd, char *cause, char *errnum,
char *shortmsg, char *longmsg)
{
char buf[MAXLINE];
/* Print the HTTP response headers */
sprintf(buf, "HTTP/1.0 %s %s\r\n", errnum, shortmsg);
Rio_writen(fd, buf, strlen(buf));
sprintf(buf, "Content-type: text/html\r\n\r\n");
Rio_writen(fd, buf, strlen(buf));
/* Print the HTTP response body */
sprintf(buf, "<html><title>Tiny Error</title>");
Rio_writen(fd, buf, strlen(buf));
sprintf(buf, "<body bgcolor=""ffffff"">\r\n");
Rio_writen(fd, buf, strlen(buf));
sprintf(buf, "%s: %s\r\n", errnum, shortmsg);
Rio_writen(fd, buf, strlen(buf));
sprintf(buf, "<p>%s: %s\r\n", longmsg, cause);
Rio_writen(fd, buf, strlen(buf));
sprintf(buf, "<hr><em>The Tiny Web server</em>\r\n");
Rio_writen(fd, buf, strlen(buf));
}
/* $end clienterror *//*
* adder.c - a minimal CGI program that adds two numbers together
*/
/* $begin adder */
#include "csapp.h"
int main(void) {
char *buf, *p, *method;
char arg1[MAXLINE], arg2[MAXLINE], content[MAXLINE];
int n1=0, n2=0;
/* Extract the two arguments */
if ((buf = getenv("QUERY_STRING")) != NULL) {
p = strchr(buf, '&');
*p = '\0';
sscanf(buf,"n1=%d",&n1); //此处决定读取格式
sscanf(p+1,"n2=%d",&n2);
}
method = getenv("REQUEST_METHOD");
/* Make the response body */
sprintf(content, "Welcome to add.com: ");
sprintf(content, "%sTHE Internet addition portal.\r\n<p>", content);
sprintf(content, "%sThe answer is: %d + %d = %d\r\n<p>",
content, n1, n2, n1 + n2);
sprintf(content, "%sThanks for visiting!\r\n", content);
/* Generate the HTTP response */
printf("Connection: close\r\n");
printf("Content-length: %d\r\n", (int)strlen(content));
printf("Content-type: text/html\r\n\r\n");
if(strcasecmp(method,"HEAD") != 0)
printf("%s", content);
fflush(stdout);
exit(0);
}
/* $end adder */